1. Field of the Invention
The present invention relates to a portable information equipment system including portable information equipment such as a portable telephone, and a battery charger of the equipment.
2. Background of the Invention
FIG. 8 is a block diagram of the structure of conventional portable information equipment such as a PHS (Personal Handy phone System).
In portable information equipment 53, an antenna 31 transmits and receives a radio wave. The radio wave received from the antenna 31 is transmitted via a switch 32 to a receive group 33 to be subjected to signal processing. The signal processed in the receive group 33 is transmitted to a voice processing portion 34 where the signal goes through voice processing to be a voice signal. Then, a receiver 35 receives the voice signal and emits a voice therefrom.
A microphone 36 receives a voice signal and transmits it to the voice processing portion 34. The voice processing portion 34 performs signal processing of the voice from the microphone 36 and transmits it to a transmit group 37. After performing signal processing of the signal from the voice processing portion 34, the transmit group 37 transmits it as a radio wave via the switch 32 to the antenna 31.
The receive group 33, the transmit group 37, and the voice processing portion 34 are controlled by a circuit control signal SC from a micro controller 40. The micro controller 40, operating on the basis of a clock generated by a crystal oscillator 41, controls a display of a liquid-crystal display portion 42, receives an input from a keyboard 43, or performs the reading and writing from/to a storage portion 44 as well as outputting the circuit control signal SC.
The liquid-crystal display portion 42 displays information, such as an input from the keyboard 43 and received electric field strength. The keyboard 43 receives information input such as a phone number, and the storage portion 44 stores personal information such as a phone number.
A rechargeable battery 45 is an operating power of the portable information equipment 53. As shown in FIG. 9, the battery 45 becomes chargeable by inserting an AC adapter 51 into an electrical outlet 52 to establish electric connections between the AC adapter 51 and the battery charger 50 as well as establishing electric connections between the portable information equipment 53 and the battery charger 50.
The AC adapter 51 converts an ac voltage obtained from the electrical outlet 52 into an appropriate dc voltage and gives it to the battery charger 50. With the dc voltage from the AC adapter 51, the battery charger 50 charges the rechargeable battery 45 in the portable information equipment 53.
The storage portion 44 consists of a high-performance/low-power volatile memory, and a nonvolatile memory that makes no loss of personal information even with insufficient holding power.
As previously described, the portable information equipment, such as a portable telephone, includes a storage portion for storing personal information such as a phone number, an address, and a schedule. This kind of portable information equipment has a built-in rechargeable battery which is charged periodically for operation.
Such portable information equipment, however, carries a risk that the personal information stored in the internal storage portion may be lost, for example when an user leave the rechargeable battery in the equipment uncharged. To prevent this, mostly applied as a memory element for storing the personal information in the portable information equipment has been a nonvolatile memory, such as a flash memory or an EEPROM (Electrically Erasable Programmable Read-Only Memory), that makes no loss of the memory contents even with low or no power voltage.
The nonvolatile memory, however, has the following problems:
(1) Its high manufacturing cost as compared with that of an ordinary volatile memory results in price increase of the portable information equipment;
(2) The use of relatively high write voltage in writing of data (still 5 to 10 V in this semiconductor world where the standard voltage is now about 3.3 V) is an disadvantage for the portable information equipment which requires reduction in power consumption;
(3) If required to include a voltage-transform device driver, the portable information equipment is upsized to be not suitable for portability; and
(4) The adoption of a high-voltage battery results in price increase of the portable information equipment.